Bile Acids and Their Receptors in Respiratory Diseases: Mechanistic and Therapeutic Perspectives

Animal bile has been used for millennia in traditional Chinese medicine as a cough suppressant and bronchodilator. As the primary functional constituents of bile, bile acids (BAs) are believed to mediate these physiological effects. Although the role of BAs in enterohepatic circulation is well-characterized, and recent advances have highlighted their immunomodulatory functions, their pathophysiological significance in the respiratory system has been largely overlooked. This review synthesizes emerging evidence on the multidimensional roles of BAs and their receptor-mediated signaling pathways, with a focus on their contribution to the pathogenesis of major respiratory diseases such as asthma, pulmonary fibrosis, and lung injury.